Fuel nozzle system

ABSTRACT

A fuel nozzle system is made available, which is arranged essentially in circular manner and is set up in such a manner that it produces a homogeneous leaner mixture on at least one outer ring and a homogeneous richer mixture on at least one inner ring, in particular a fuel/oxidizer mixture.

The invention relates to a burner having a reduced flame temperature.

A burner having a burner head, which essentially has a tubular channel in which the oxygen carrier, for example air, flows out by way of a fan, and mixes, in this regard, with the fuel, for example gas, which is guided into a tubular channel by way of a distributor system, serves for combustion of the fuel mixed with an oxygen carrier. An ignition device serves for ignition of the mixture of oxygen carrier and fuel, thereby initiating combustion.

Such burner heads represent a burden on the environment, since they emit nitrogen oxides No_(x) produced during combustion into the atmosphere. For this reason, burners having burner heads with which the production of these oxides can be reduced have already been developed.

A burner head is known from the Italian patent application 85 622—A/90, in which reduction of the nitrogen oxides is achieved with the aid of distributor devices during feed of the fuel. The distributor is situated in the interior of the front part of the feed pipe for the combustion air and consists of ring-shaped interstices that run at a right angle to the axis of the feed pipe and are delimited by rings that are coaxial to one another, which rings are connected with one another by way of spacer elements.

A burner consisting of a block is known from the further Italian patent application VI 91 A 42, in which the nitrogen oxides are decomposed in that a part of the flue gases produced during combustion is passed back into the interior of the burner head.

In the further Italian patent application XI 91 A 166, a burner is proposed in which a row of openings is worked into the outer circumference of the feed channel for the combustion air, so as to reduce the nitrogen oxide production.

A burner head for burners having a tubular body for feed of an oxygen carrier into a combustion chamber is known from DE 195 42 73 B4, in which one or more pipelines for feed of a fuel into the combustion chamber is/are provided, wherein the pipelines run in the tubular body and are supplied with the fuel by way of a feed channel. In addition, a converging transition piece is provided at the end of the tubular body, which piece projects into the combustion chamber, wherein the convergence is directed into the interior of the combustion chamber. Furthermore, at least one ignition device, which lies in the tubular f-body in the vicinity of the converging transition piece, is provided, wherein the exit opening of each pipeline for feed of the fuel lies within a zone of the tubular body that is delimited by the convergence of the transition pieces and lies in the inclined wall surface of the transition piece, and thereby the fuel flow goes essentially outward and into the zone of greater flow velocity of the oxygen carrier stream. In this manner, the gas flow is directed against the outer region of the air stream, which is accelerated when passing through the converging transition piece and in this way entrains the gas flow far into the interior of the combustion chamber. At the same time, the acceleration of the air stream brings about a partial vacuum in the region of the combustion chamber, so that part of the flue gases produced during combustion is passed back into the flame. As a result, a reduction in the flame temperature and a lower nitrogen oxide concentration are achieved.

Fundamentally, combustion apparatuses of the stated type are known, which convert chemical energy to thermal energy during a combustion process. In this combustion process, at least one oxidation agent, preferably air or oxygen, is combusted with a fuel, in the combustion chamber, in a continuous reaction, giving off heat. The heated waste gases are emitted to the free surroundings by way of the opening, and can be utilized, for example, in heating systems of all kinds, drying systems, thermal post-combustion devices, environmental systems, annealing ovens or in other systems of process technology. Possible fuels are, for example, commercially available, purified gases such as town gas, grid gas, natural gas or liquid gas, as well as mixtures of them. Heating oil, petroleum, and other liquid or paste-form fuels can also be combusted.

The burners generally known from the state of the art can be divided into two categories. The first category includes burners in which the oxidation agent is sprayed into the combustion chamber together with the fuel, as a mixture. Such burners are also referred to as pre-mix burners. Burners of the second category, in contrast, have a separate feed of the oxidation agent and of the fuel, up to the combustion chamber, so that mixing of the two substances only takes place in this chamber. The burners of the first category do have the advantage that the mixture of oxidation agents and fuel is available in the combustion chamber in a very homogeneous mixture, but the disadvantage is that absolute safety with regard to flashbacks does not exist. Such flashbacks are excluded in the case of burners of the second category, due to the separate feed of the oxidation agent and the fuel. However, the homogeneity of the mixture in the combustion chamber is not optimal. In any case, it is worse than in the case of the mixture achieved by burners of the first category.

The invention therefore has as its goal to combine the advantages of burners of the second category with the advantages of burners of the first category, in other words to reliably preclude flashbacks, on the one hand, but at the same time to ensure great homogeneity of the mixture and thereby to lower not only the flame temperature but also the discharge of nitrogen.

The most optimal possible combination of safety and optimal combustion is supposed to be achieved.

This task is accomplished with a burner of the type described initially, according to the invention, having the characteristics of claim 1.

A fuel nozzle system is made available, which is arranged essentially in circular manner and is set up in such a manner that it produces a homogeneous lean mixture on at least one outer ring, and a homogeneous richer mixture, in particular a fuel/oxidizer mixture, on at least one inner ring. For this purpose, it is provided, in a first embodiment, that smaller exit nozzles are present on the at least one outer ring, and larger exit nozzles are provided on the at least one inner ring. These two mixtures are supposed to burn separately from one another, to the extent possible, during combustion, so as to keep the flame temperature low. For this purpose, it is furthermore provided that the leaner mixture produced on the at least one outer ring and the richer mixture produced on the at least one inner ring flow into a common combustion chamber, in which optimal combustion takes place.

It is also provided that the leaner mixture produced on the at least one outer ring and the richer mixture produced on the at least one inner ring are jointly supplied to the combustion in the combustion chamber.

In an alternative embodiment, it is provided that a homogeneous lean mixture can be adjusted on the at least one outer ring, by means of control and/or regulation devices, valves, flaps or the like, and a homogeneous richer mixture can be adjusted on the at least one inner ring.

In a further, advantageous embodiment, the fuel nozzle system is configured in such a manner that the exit direction of the substances, in particular, however, of the oxidizer, can be influenced in targeted manner. The resulting different spin or differently directed mass flow leads to a separation that lasts as long as possible, in other words separation or non-mixing of the inner homogeneous rich mixture and of the outer homogeneous lean mixture during combustion. In this way, the flame temperature and thereby also the nitrogen oxide formation is clearly reduced in both regions, wherein with reference to the overall process, in which the inner and the outer region are considered jointly, nevertheless optimal, nearly stoichiometric combustion takes place.

Furthermore, it is provided that the direction of the substances, in particular of the fuel, can be influenced by means of a slanted position of the exit nozzles. It has been found that outflow of the fuel or gas at a slant to the air spin also has particularly positive effects on the homogeneity of the corresponding fuel/oxidizer mixture.

As a further embodiment, it is proposed that a pipe that has at least a double wall is provided between the inner and the outer ring, through which pipe the fuel flows. The advantage of this solution consists in that the “slipstream” of the double-wall pipe prevents mixing of the inner, richer region toward the outer, lean region.

In a further embodiment, two concentric pipes having at least double walls are provided, through which the fuel flows. By means of the first gas channel in the inner pipe and the second gas channel in the outer pipe, it is possible to control these separately by means of valves or control devices, flaps or the like, and thereby to further optimize the result.

A device for igniting the burner is provided in the cross-section of a pipe that has at least a double wall. In the case of such an arrangement, these ignition apparatuses, in particular ignition electrodes, cause the least disruption for the flow of the gas and of the oxidizer, and therefore do not lead to deficient homogeneity.

Furthermore, a device for flame monitoring, in particular a UV flame sensor, an IR flame sensor or an ionization electrode can also be arranged in the cross-section of a pipe having at least a double wall. This also leads to the result that the flow is hindered as little as possible.

Furthermore, it is provided that the velocity of the substances, in particular of the oxidizer in the fuel nozzle system can be influenced in targeted manner. It is advantageous to allow the outside air or the oxygen to flow somewhat faster than on the inside.

It is also practical to be able to influence the velocity of the substances, in particular of the fuel, in targeted manner. Better mixing is obtained by means of a higher velocity. Also, a further improvement in homogeneity can be achieved by means of a distribution of a plurality of exit openings of the fuel nozzle system over one or more planes.

In order to make the most simple and widespread use of the new burner possible, it is provided that this burner is configured to be compatible with commercially available industrial burners. Its production can be simplified, or actually made possible, in the first place, by means of additive production methods. In the following, the invention will be explained in greater detail, as an example, using the drawings. These show, in

FIG. 1 an overall view of the burner, cut in half;

FIG. 2 an overall view of the fuel nozzle system from the front;

FIG. 3 an overall view of the fuel nozzle system from the rear;

FIG. 4 a cross-section through a fuel nozzle system according to the invention, having smaller exit nozzles arranged on an outer ring and larger exit nozzles arranged on an inner ring;

FIG. 5 a perspective view of the fuel nozzle system;

FIG. 6 an alternative embodiment;

FIG. 7 a detail with exit nozzles set at a slant.

A fuel nozzle system 5 of a burner 1 indicated in general with 1 has a housing 2 having a combustion pipe 3, which has an opening 4 at an end facing away from this housing 2. The housing 2 has two channels 6, 7, separated from one another, through which different substances flow, in particular a fuel and an oxidizer, which mix in a combustion chamber 8, not shown in any detail.

The fuel nozzle system 5 is arranged essentially in circular manner, and is set up in such a manner that it produces a leaner mixture on at least one outer ring 12 and a richer mixture on at least one inner ring 13, in particular a fuel/oxidizer mixture. For this purpose, it can have smaller exit nozzles 14 on at least one outer ring 12 and larger exit nozzles 15 on at least one inner ring 13.

Alternatively, fewer exit nozzles 14 can be present on the at least one outer ring 12 and more exit nozzles 15 can be present on the at least one inner ring 13 than on the other ring 12, 13, in each instance.

The exit direction of the substances, in particular of the fuel, can be influenced in targeted manner by means of setting the exit nozzles 14, 15 at a slant or in some other suitable manner, for example by means of spin elements 9 and/or guide panels 11. Also, it is possible to set a leaner mixture on the outer ring 12 and a richer mixture on the inner ring 13 by means of control and/or regulation devices, valve flaps or the like, which are not shown in any detail. In a similar manner, the velocity of the substances, in particular of the oxidizer and/or fuel, can be influenced in targeted manner.

In a further embodiment, a plurality of exit openings 14, 15 of the fuel nozzle system 5 is distributed over one or more planes 16, 17.

In a further embodiment, a pipe 18 having at least a double wall, through which pipe the fuel flows, is situated between the inner and the outer ring 12, 13. Also, at least two concentric pipes 18, 18′, which have at least a double wall and through which the fuel flows can be provided.

A device 20 for ignition of the burner 1 can be arranged in the cross-section of a pipe 18, 18′ having at least a double wall. Likewise, a device 21 for monitoring the flame of the burner 1 is provided. Finally, it is possible to arrange a central pipe 22 for injection of a further fuel, an inert gas and/or a reduction agent, in particular urea, in the center of the circular arrangement, directly in the combustion chamber 8.

Of course, the invention is not restricted to the exemplary embodiments shown. Further embodiments are possible without departing from the basic idea.

REFERENCE SYMBOL LIST

-   1 burner -   2 housing -   3 combustion pipe -   4 opening -   5 fuel nozzle system -   6 channel, fuel -   7 channel, oxidizer -   8 combustion chamber -   9 spin element -   11 guide panel -   12 outer ring -   13 inner ring -   14 exit nozzle -   15 exit nozzle -   16 plane -   17 plane -   18 double-wall concentric pipe -   18′ double-wall concentric pipe -   20 ignition -   21 flame monitoring -   22 central pipe 

1. A burner system having a burner (1) having a housing (2), on which a combustion pipe (3) is arranged, and a combustion chamber (8) wherein the combustion pipe (3) has an opening (4) on the end facing away from the housing (2), and wherein the housing (2) has at least two channels (6, 7) that are separated from one another, and are set up in such a manner that different substances, in particular a fuel and an oxidizer, flow through them, and mix in the combustion chamber (8), wherein the substances empty into a fuel nozzle system (5) that is arranged in essentially circular manner, and is set up in such a manner that it produces a leaner mixture on at least one outer ring (12), by means of first exit nozzles, and a richer mixture on at least one inner ring (13), in particular a fuel oxidizer mixture, by means of second exit nozzles.
 2. The burner system according to claim 1, wherein it is set up in such a manner that the leaner mixture produced on the at least one outer ring (12) and the richer mixture produced on the at least one inner ring (13) flow into a common combustion chamber (8).
 3. The burner system according to claim 1, wherein it is set up in such a manner that the leaner mixture produced on the at least one outer ring (12) and the richer mixture produced on the at least one inner ring (13) are jointly passed to the combustion.
 4. The burner system according to claim 1, wherein it is set up in such a manner that the substances empty into a fuel nozzle system (5) that is arranged in essentially circular manner and has smaller (14) exit nozzles on at least one outer ring (12) and larger exit nozzles (15) on at least one inner ring (13).
 5. The burner system according to claim 1, wherein the substances empty into a fuel nozzle system (5) that is arranged in essentially circular manner and has fewer first exit nozzles (14) on at least one outer ring (12) and more second exit nozzles (15) on at least one inner ring (13) than on the other ring (12, 13), in each instance.
 6. The burner system according to claim 1, wherein the substances empty into a fuel nozzle system (5) that is arranged in essentially circular manner, wherein a lean mixer can be set on at least one outer ring (12), by means of control and/or regulation devices, valves, flaps, and a richer mixture can be set on at least one inner ring (13).
 7. The burner system according to claim 1, wherein the fuel nozzle system (5) is configured in such a manner that the exit direction of the substances, in particular of the oxidizer, can be influenced in targeted manner.
 8. The burner according to claim 4, wherein the direction of the substances, in particular of the fuel, can be influenced by means of a slanted position of the first and second exit nozzles (14, 15).
 9. The burner system according to claim 1, wherein the fuel nozzle system (5) is configured in such a manner that the velocity of the substances, in particular of the oxidizer, can be influenced in targeted manner.
 10. The burner system according to claim 1, wherein the fuel nozzle system (5) is configured in such a manner that the velocity of the substances, in particular of the fuel, can be influenced in targeted manner.
 11. The burner system according to claim 1, wherein a plurality of exit openings (14, 15) of the fuel nozzle system (5) are distributed over one or more planes (16, 17).
 12. The burner system according to claim 4, wherein the exit nozzles (14, 15), in particular the smaller (14) and larger exit nozzles (15) lie in different planes (16, 17).
 13. The burner system according to claim 1, wherein it is set up in such a manner that an at least double-wall pipe (18) is provided between the inner and the outer ring (12, 13), through which pipe the fuel flows.
 14. The burner system (1) according to claim 1, wherein it is set up in such a manner that two at least double-wall concentric pipes (18, 18′) are provided, through which the fuel flows.
 15. The burner system according to claim 1, wherein a device (21) for ignition of the burner (1) is provided in the cross-section of an at least double-wall pipe (18, 18′).
 16. The burner system according to claim 1, wherein a device (21) for monitoring the flame of the burner system is provided in the cross-section of an at least double-wall pipe (18, 18′).
 17. The burner system according to claim 1, wherein a central pipe (22) for injection of a further fuel, an inert gas and/or a reduction agent, in particular urea, directly into the combustion chamber (8) is provided in the center of the circular arrangement.
 18. The burner system according to claim 1, wherein the fuel nozzle system is produced using an additive production method.
 19. The burner system according to claim 1, wherein it is configured to be compatible with commercially available industrial burners. 